Prevalence and Prognostic Implications of PSA Flares during Radium-223 Treatment among Men with Metastatic Castration Resistant Prostate Cancer.

Radium-223 (Ra233) prolongs the survival of men with symptomatic bone-predominant metastatic castration-resistant prostate cancer (mCRPC). However, prostate-specific antigen (PSA) response patterns are not closely associated with Ra223 therapy outcomes. Herein, we sought to analyze the impact of Ra223-induced PSA flares on patient outcome. Using a retrospective cohort study of Ra223 treatment in four Ontario/Canada cancer centres, we identified 134 patients grouped into sub-cohorts according to distinct PSA response patterns: (i) initial PSA flare followed by eventual PSA decline; (ii) PSA response (≥30% PSA decrease within 12 weeks of treatment); and (iii) PSA non-response. We analyzed patient characteristics and outcome measures, including overall survival (OS), using the Kaplan-Meier method and log-rank testing. PSA flares were observed in 27 (20.2%), PSA responses in 11 (8.2%), and PSA non-responses in 96 (71.6%) patients. Amongst PSA flare patients, 12 presented with post-flare PSA decreases below baseline and 15 with PSA decreases below the flare peak but above baseline. Although only six flare patients achieved ≥30% PSA decreases below baseline, the median OS of all flare patients (16.8 months, 95% CI 14.9-18.7) was comparable to that of PSA responders and non-responders (p = 0.349). In summary, around 20% of mCRPC patients experience Ra223-induced PSA flares, whose outcome is similar to that of men with or without PSA responses. Further studies are needed regarding suitable biochemical surrogate markers of response to Ra223.

Journal of clinical medicine. 2023 Aug 28*** epublish ***

Amanjot Sidhu, Nabeeha Khan, Cameron Phillips, Juan Briones, Anil Kapoor, Pawel Zalewski, Neil E Fleshner, Edward Chow, Urban Emmenegger

Sunnybrook Odette Cancer Centre, Toronto, ON M4N 3M5, Canada., Juravinski Cancer Centre, Hamilton, ON L8V 5C2, Canada., Durham Regional Cancer Centre, Oshawa, ON L1G 2B9, Canada., Princess Margaret Cancer Centre, Toronto, ON M5G 2M9, Canada.